Technically, plagarism is a civil offense, so Mr. Krabs wouldn't necessarily be arrested for stealing the motto from the other hotel. However, he can be sued for it, if the other hotel found out. And about the scene where Mr. Krabs first gives the plate of cookies to Squidward, he could have changed from his black suit to an employee's uniform before going back up to the floor where Squidward's room is located.